| Skew Limits | ||||
| Device | Driver | Receiver | Application | |
| SN75976A1 | 8ns | 9ns | Fast-SCSI | |
| SN75976A1 | 4ns | 5ns | Fast-20 SCSI | |
The industry's first nine-channel differential transceiver for SCSI bus applications achieving the speed requirements of Fast-20 SCSI, at 20 million transfers per second, is now available from TI. The SN75976A is ideally suited for applications such as Hard Disk drives and host adapter add-in boards which interface a computer system to a differential SCSI I/O subsystem.
The demands upon computer systems I/O bus bandwidth is increasing with the amount and number of users of the data on video-on-demand, video and network servers, and RAID systems. Additional headroom has been achieved with the evolution of the parallel SCSI bus to its newest version - Fast-20 SCSI (formerly Ultra-SCSI).
SCSI is a parallel data bus meaning data is transferred over the cable more than one bit at a time. Time variation of the defining voltage transitions is typically called skew and sometimes jitter. To account for skew and provide inter-operability between Fast-20 SCSI nodes, the standards specify minimum setup and hold times of the data with relation to the clocking signals. This requires that the delay times of each line circuit be within a narrow range, the width of which determines the worst-case skew, or skew limit. The SN75976A is offered in two skew limits. (See table)
The SN75976A is available in the Thin Shrink Small-Outline Package (TSSOP) with 20 mil lead pitch. This reduces the board area by about 30% over that required by the Shrink Small-Outline Package (SSOP) of the original 'LBC976. For faster time to market with a Differential Fast-20 product, the '976A is also offered in the SSOP for a drop-in upgrade to existing designs.
Vol 13, September, 1995
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